Recently, it has been found that the levels of CCl2 and CCl3 in the peripheral blood of patients with rheumatoid arthritis are increased and are positively correlated with rheumatoid factor, which means they have good predictive value for the occurrence, curative effect and prognosis of rheumatoid arthritis (Guo et al., 2021). Here, CCL2 is linked to rheumatoid arthritis.